Abstract

Am. J. Physiol. 260 (Endocrinol. Metab. 23): E883-E890, 1991.-Eight highly trained cyclists were studied during exercise after glycogen depleti (test A) and during (CHO) loading (test B). In test B subjectswere ableto complete 2 h of exerciseat 70-75% maximal workload (Wmax),whereas the initial intensity of 70% W,,, had to be reducedto 50% in test A. Plasma ammia increased more rapidly, and plasma alanine, glutamate, and glutamine were lower in test A. Exercise causeda 3.6-fold increasein the proporti of active branchedchain 2-oxo dehydrogenase (BC) complex in musclein test A. No activati occurred in test B. There was an inverse correlati between the activity of the BC complex and the glycogen ctent of the postexercisebiopsies.Exercise did not causechanges the musclectent of ATP, ADP, AMP, IMP, in hypoxanthine, and lactate. It is ccluded that CHO loading abolishesincreases branched-chain (BCAA) oxin idati during exerciseand that part of the ammia producti during prolged exerciseoriginates from deaminati of s. The data appear to cfirm the hypothesis (A. J. M. Wagenmakers, H. Coakley, and R. H. T. Edwards. Int. J. J. Sports Med. 11: SlOl-S113, 1990) that accelerati of the BCAA transferasereacti may drain the tricarboxylic cycle and that glycogen is a carb chain precursor

Journal

AJP - Endocrinology and Metabolism
– The American Physiological Society